Portable information terminal devices such as mobile phones include devices provided with a camera for generating image data by photographing an object. In some of the portable information terminal devices of this kind distributed to the market recently, an authentication process (so-called face authentication) is carried out by guiding a user to photograph a face image by a camera during operation and comparing characteristic information such as a shape and size of eyes, nose, mouth and outline extracted from a photographed face image with user characteristic information which is stored in advance in a memory provided in the portable information terminal devices. Only when results of the authentication process show that a matching degree between characteristic information extracted from a photographed image and user characteristic information exceeds an authentication threshold value, a person who carries out operation at that time is determined to be a true user and authorized to execute processes thereafter, so that security improvement and privacy protection can be enhanced (ex. refer to Patent Document 1).
In general, an image photographed in an authentication process is not stored in a memory, and characteristic information extracted from the image is exclusively stored in a memory and compared with registered characteristic information. Here, if it is allowed to store an image photographed in an authentication process as history information when a person who differs from a true user such as, for example, a person who operates a stolen portable information terminal device tries to use the portable information terminal device illegally, the illegal user can be identified from the stored image after the portable image terminal device is retrieved, which is convenient. Therefore, various kinds of techniques have been proposed in the technical field of this kind in order to store images photographed in an authentication process as history information when the authentication process has failed (ex. refer to Patent Documents 1 to 3).    [Patent Document 1] Japanese Unexamined Patent Publication No. 2000-278658    [Patent Document 2] Japanese Unexamined Patent Publication No. 2005-115485    [Patent Document 3] Japanese Unexamined Patent Publication No. 2005-084991